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        var grade = prompt("请输入分数");
        switch (parseInt(grade / 10)) {
             case 10:
                alert("你的成绩等级为优秀");
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             case 9:
                alert("你的成绩等级为优秀");
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             case 8:
                alert("你的成绩等级为良好");
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             case 7:
                alert("你的成绩等级为良好");
                break;
             case 6:
                alert("你的成绩等级为良好");
                break;
             default:
                alert("你的成绩等级为不及格，继续加油哦！");
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